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Ionizing feedback from an O star formed in a shock-compressed layer

Whitworth, Anthony ORCID:, Priestley, Felix and Geen, S T 2022. Ionizing feedback from an O star formed in a shock-compressed layer. Monthly Notices of the Royal Astronomical Society 517 (4) , pp. 4940-4949. 10.1093/mnras/stac2955

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We develop a simple analytical model for what happens when an O star (or compact cluster of OB stars) forms in a shock-compressed layer and carves out an approximately circular hole in the layer, at the waist of a bipolar H II region (H IIR). The model is characterized by three parameters: the half-thickness of the undisturbed layer, ZLAYER⁠, the mean number density of hydrogen molecules in the undisturbed layer, nLAYER⁠, and the (collective) ionizing output of the star(s), N˙LyC⁠. The radius of the circular hole is given by WIF(t)∼3.8pc[ZLAYER/0.1pc]−1/6[nLAYER/104cm−3]−1/3[N˙LyC/1049s−1]1/6[t/Myr]2/3⁠. Similar power-law expressions are obtained for the rate at which ionized gas is fed into the bipolar lobes, the rate at which molecular gas is swept up into a dense ring by the shock front that precedes the ionization front, and the density in this dense ring. We suggest that our model might be a useful zeroth-order representation of many observed H IIRs. From viewing directions close to the mid-plane of the layer, the H IIR will appear bipolar. From viewing directions approximately normal to the layer, it will appear to be a limb-brightened shell but too faint through the centre to be a spherically symmetric bubble. From intermediate viewing angles, more complicated morphologies can be expected.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Advanced Research Computing @ Cardiff (ARCCA)
Physics and Astronomy
Publisher: Royal Astronomical Society
ISSN: 0035-8711
Date of First Compliant Deposit: 4 January 2023
Date of Acceptance: 11 October 2022
Last Modified: 17 Jun 2024 14:20

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